This study was undertaken to evaluate the right ventricular myocardial systolic function and its relation to the fetal volume and pressure overload in recipient twin of twin to twin transfusion syndrome with speckle tracking echocardiography. Longitudinal peak systolic strains of the right ventricle were measured by speckle tracking echocardiography in 17 patients with twin-to-twin transfusion syndrome (TTTS) and 19 normal monochorionic diamniotic pregnancies. The right ventricular free wall thickness in recipient twin (0.43 +/- 0.14 cm) was significantly larger than that in the donor (0.21 +/- 0.04 cm, p < 0.05) and the control group (0.18 +/- 0.03 cm, p < 0.05 for larger twin and 0.17 +/- 0.02 cm, p < 0.05 for smaller twin). Although there were no significant differences in the right ventricular fractional shortening and cavity area percent change among control and the TTTS groups, the absolute value of peak systolic strains of ventricular septum, right ventricular free wall and global right ventricle in recipients were all significantly lower than those of the donors and the control group. Besides, the global right ventricular peak systolic strain correlated well with gestational age adjusted right ventricular free wall thickness (r = 0.65, p = 0.04) but not with gestational age adjusted right ventricular end-diastolic dimension (r = 0.38, p = 0.28) and cavity area percent change (r = 0.33, p = 0.35). Right ventricular systolic dysfunction measured with decreased right ventricular peak systolic longitudinal strain exists despite the absence of diminished fractional shortening and cavity area percent change and this reduced systolic function correlates with the right ventricular pressure overload as shown by increased right ventricular free wall thickness. (E-mail: ybdeng2007@hotmail.com) (C) 2012 World Federation for Ultrasound in Medicine & Biology.